“ In the Lake District the great volcanic series of Borrowdale, green slates and porphyries, 8000 to 9000 ft. in thickness, lies on this horizon; and in the Cross Fell area the Milburn beds of the Skiddaw slates (see Arenig) appear to be of the same age. In Scotland the Llandeilo group is represented by the Glenkiln shales, black shales and yellowish mudstones with radiolarian cherts and volcanic tuffs ”

“ Conularia and Hyolithes among the Pteropods; the Cephalopods are represented by Orthoceras and Cyrtoceras. The green roofing slates and plumbago (graphite) of the Lake District are obtained from this group of rocks, (see Ordovician) . ”